Differential-pressure gage.



C. H. CRAIG, JR. DIFFERENTIAL PRESSURE GAGE.

AEPLIUATION FILED JAN.-30, 1907.

Patented Decf29, 1908.

Mii v3 www thec UNITED sTATns N'PATENT konirica..

CHARLES H. CRAIG, JR., OF BOSTON, MASSACHUSETTS, ASSIGNOR TO AMERICAN STEAM GAUGE AND VALVE MANUFACTURING COMPANY, OF BOSTON, MASSACHUSETTS, A COR- YPORATION OF NEW JERSEY.

DIFFERENTIAL-PRESSURE GAGE.

Specification of Letters Patent.

Patented Dec. 29, 1908.

Application led January, 1-907. Serial No. 354:;858.

To :all whom 'it may concern:

Be it known that I, CHARLES H. CRAIG, Jr., oi' Boston, in the county of Suffolk and State of' Massachusetts, have invented certain new and useful Improvements in Differential-Pressure Gages, of which the following is a specification.

This invention relates to pressure gages -yfor indicating directly the differences loetween pressures, and has for its object to provide a gage of this character of great sensitiveness, and one of which the degree of sensitiveness can be adjusted so that relatively slight diii'erences of pressure can be accurately indicated and read.

Of the accompanying drawings,-Figure l represents an elevation, partially in section, of a gage embodying the principles of my invention. Fig. 2 represents a modification of the pressure-actuated means. Fig. 3 represents a further modification of the pressure-actuated means.

The same reference characters indicate the same parts in all the figures.

a represents the casing of a gage into which are screwed cylinders b and c. The outer portions of these cylinders form chambers d and e, respectively, which have threaded inlets f and g, whereby a fluidconducting pipe ma `be connected. EX- tendng across each o the chambers is a diaphra m forming a movable upper wall of gember, and to the diaphragms are connected rods a and y' which are pivotally connected to a beam k which is plvoted at Z.

The connection of the diaphragms with the rods is, made through clamps m and n of which the former is secured to the rod, while the latter lies .on the under side of the diaphragm and is connected with the first clamp by a bolt o. These clamps are formed with spherical surfaces where they abut againstthe diaphragm in order that their edges may not cut the latter when displaced. Springs p are located in the tubes o and c and are adjusted by means of screw-caps g and r threaded upon the ends of the tubes.

A lug s is formed upon one end of the beam k or on the head of the rod z', and is connected by means of a link .t with a pivoted lever u having a gear segment o which meshes with a pinion on the spindle of a hand or indicator w. By means ot the gear segment, the hand is swung over a dial Pressures being admitted to the chambers beneath the diaphragms, act upon the beam 7c on opposite sides of the pivot of the latter so that eachppressure opposes the other, and no motion whatever will be given to the beam if the pressures are even. In case one pressure is greater than that of the other, the beam will be movedv by the greater pressure, forcing the diaphragm in the other chamber in opposition to the fluid pressure acting thereon. Then the hand is moved proportionally to the dierence in pressure until the motion is checked by the increasing resistance of one of the springs y). Thus the differences between two pressures are directly indicated by the hand, there being no indication of the absolute vaiue of either pressure alone.

In Fig. 2, a modification which consists in substituting a piston L in the cylinders d and e is shown. The pressure fluid is admitted through inlets g into the chamber below the piston and tends to force the latter upward against the resistance of the spring p. In this form of the device, the tubes b and 0, springs p, rods z' and y', beam lc and screw-caps g and 7' are the same as previously described. The connections of the pistons with the rods z' and j are made by bearing cones z" entering the conical sockets in rods h2 formed upon the pistons.

In Fig. 3 is shown a modification by which the differences between very slight pressures may be measured. This form dispenses with the spring p and to take the place of the latter there is substituted va metal diaphragm h3 which is resilient. The diaphragm has a number of annular corrugat1ons`to increase the amount of fiexure which is possible to give it. It is secured to the rod z' in the same manner as is the diaphragm la.. The fiexible diaphragm h3 interposcs comparatively little resistance to displacement, and therefore is adapted to move the indicator by a comparatively large amount in registering very small pressures.

The three forms of pressure means are alike in this, that each consists of a chamber having a movable wall, since the diaphragms z. and k3 and the piston L are the displaceable walls of the pressure chambers in which the fiuid is admitted. Each of these movable acts upon the indicator.

Iclaimz-h v l. A gage consisting of a plurality of chambers adapted to simultaneously receive` fluid under pressure and each provided with amovable wall displaceable by pressure, said walls being so positioned that the pressure exerted against each is in the same direction, an indicator and a differential device connected Awith saidwalls and said indicator whereby the latter will disclose the diiferences between the pressures acting upon said device.

2. A gage comprising a plurality of chambers adapted/to simultaneously receive fluid under pressure and each provided with a movable wall displaceable by pressure, said walls being so positioned that the pressure against each is in the same direction, a rod secured to the movable wall of ea'ch chamber, an indicator, and a dili'erential device connected with said rods and said indicator, whereby the latter will disclose the dii'er ences between vthe pressures acting upon them.

3. A gage consisting of a plurality of chambers adapted to simultaneously receive fluid under pressure and each provided with 'a movable Wall/displaceable by. pressure, said Huid under pressure and each provided withv a movable wall displaceable by pressure, said walls being so positioned that'the pressure exerted against each is in the same d1rection, a pivoted bar connections between the same and each of the movable chamber walls, whereby the pressures thereof act opposingly on the bar giving it a motion proporv tional to the differences 1n such pressures,

and means for returning said bar to its nor'- mal position.

5. A gage( consisting of a plurality of chambers adapted to receive fluid under pressure, each having a movable wall dis-` placeable by pressure, a pivotedbar, and connections on opposite sides of the pivot of .the bar with the movable chamber walls,

whereby the' pressures of the latter are chambers adapted to receive` fluid under pressure, a movable wall in each chamber displaceable by variations in pressure of the fluid therein trom a predetermined amount, constructed and arranged sol as to oppose a yielding resistance to such displacement, mo-

tion-transmitting members connected to said walls, and a pivoted connecting member attached to each of the transmitting members in such manner that positive pressures ap? plied to the latter may, at one .and the 'same time, urge the connecting member to turn in opposite directions about its pivot.

8. A gage consisting of ay plurality of chambers adapted to simultaneously receive fluid under pressure and each provided with a movable wall displaceable by pressure, said walls being so positioned that the pressure exerted against each is in the same d1rection, an indicator, and connections between said displaceable wall and indicator wholly ex- -A fternal to the chambers, operating proportionally to the differences 'between the several fluid pressures for moving the indicator to showv such differences.

9. A gage consisting of a plurality of chambers adapted to receive fluid under pressure from different sources, a movable I wall foreach chamber displaceable by pressure, a pivoted bar, connections with the bar and the several displaceable Walls arranged so as to tend to move the bar at the same time in opposite directions about its pivot, a rotary indicator and a segment engaged therewith and oscillated by-movements of said bar, whereby the indicator is causedto move proportionately to the differences in the pressures.

In testimony whereof I have `aiiiizedjmy signature', in presence of two witnesses.

CHARLES H. CRAIG, JR.

Witnesses: v

A. C. RATIGN, ARTHUR H. BRowN. 

